Forty acutely psychotic patients were treated either with flupenthixol drops or haloperidol drops in an open, 28-day controlled study. The flupenthixol group comprised 11 schizophrenic, 8 manic, and 1 paranoid patient and there were 10 schizophrenic, 5 manic, and 5 paranoid patients in the haloperidol group. Mean daily dosage was approximately 112 mg flupenthixol and 18 mg haloperidol. Clinically, both drugs showed an antipsychotic effect. In the schizophrenic patients there was a definite trend towards a more rapid relief of the psychotic symptoms after flupenthixol treatment. In contrast to haloperidol, flupenthixol showed a mood elevating effect and an effect on the negative symptoms, e.g. emotional withdrawal, motor retardation, blunted affect, and disorientation. With both drugs, the most troublesome side-effects were extrapyramidal in nature. Initially, they were more common in the flupenthixol group: later the incidence was similar.